<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        .g-container {
            width: 100vw;
            height: 100vh;
            display: grid;
            place-items:center;
        }

        .g-box {
            width: 200px;
            height: 200px;
            border: 1px solid #ccc;

        }
    </style>
</head>
<body>
    <div class="g-container">
        <div class="g-box"></div>
    </div>
</body>
</html>